1. Field of the Invention
The preset invention relates to an arrangement structure for an umbilical member such as a cable and/or air tube, used in a parallel link robot.
2. Description of the Related Art
As means for positioning a movable part having an end effector in three-dimensions, a delta-type parallel link robot is well known. For example, FIG. 6 is a perspective view of a conventional parallel link robot. As shown in FIG. 6, conventional parallel link robot 100 has a base part 110, a movable part 120 and three link parts 200a, 200b and 200c for coupling base part 110 with movable part 120, wherein movable part 120 is provided with an attachment member 190 for an end effector (not shown).
Link part 200a is constituted by a drive link 210a extending from base part 110, and two passive links 220a and 230a, wherein the passive links are coupled to each other by means of a spherical bearing. Base part 110 has an actuator 130a for driving drive link 210a. The other link parts 200b and 200c have the same constitution as link part 200a. By individually controlling actuators 130a, 130b and 130c of respective link parts 200a, 200b and 200c, movable plate 120 is moved with three degrees-of-freedom (or first, second and third axes), whereby the movable plate can be positioned at an arbitrary place.
As described above, the conventional parallel link robot is constituted by the base part, the movable part, and the drive link and the passive link which couple the base part to the movable part. Three pairs of drive links and passive links are provided and each pair is individually controlled. Due to this, the movable part can be moved with three degrees-of-freedom.
In the parallel link robot of FIG. 6, a mechanism may be arranged to change the orientation of attachment member 190 to which the end effector is attached, and an actuator for driving the mechanism may be further added. For example, FIG. 2 of Japanese Unexamined Patent Publication (Kokai) No. 2011-088262 discloses a configuration wherein an additional actuator is positioned between two passive links.
When the additional actuator is used, it is necessary to arrange an umbilical member for the actuator, such as a cable or air tube, from the base part, and connect to the actuator. Therefore, it is necessary to arrange the umbilical member so as to not obstruct the motion of the robot. For example, FIG. 1 of Japanese Unexamined Patent Publication (Kokai) No. 2004-223635 discloses a configuration wherein wire/pipe 11 is held by a clamp member arranged on universal joint 5, and is connected to joint 20 of spindle head 2 via clamp member 19 arranged on ball screw 4. Further, FIG. 4 of Japanese Unexamined Patent Publication (Kokai) No. 2004-223635 discloses a configuration wherein wire/pipe 11 is connected spindle head 2 from clamp member 31 extending through ceiling part 7 via clamp member 32.
In FIG. 1 of Japanese Unexamined Patent Publication (Kokai) No. 2004-223635, the umbilical member projects outward from the parallel link mechanism, whereby a substantial area occupied by the mechanism becomes larger. Therefore, the umbilical member may interfere with external equipment, and may be damaged. On the other hand, in FIG. 4 of Japanese Unexamined Patent Publication (Kokai) No. 2004-223635, the umbilical member is contained within an interior area of the parallel link mechanism. However, as shown in FIG. 5, excessive stress may be applied to the umbilical member when the link mechanism is operated over a wide range.